<template>
	<view>
		<view class="scroll-view-container">
			<!-- 左侧的滚动视图区域 -->
			<scroll-view class="left-scroll-view" scroll-y :style="{ height: wh + 'px' }">
				<block v-for="(item, i) in cateList" :key="i">
					<view
						:class="['left-scroll-view-item', i === active ? 'active' : '']"
						@click="activeChanged(i)"
					>
						{{ item.cat_name }}
					</view>
				</block>
			</scroll-view>
			<!-- 右侧的滚动视图区域 -->
			<scroll-view
				:scroll-top="scrollTop"
				class="right-scroll-view"
				scroll-y
				:style="{ height: wh + 'px' }"
			>
				<view class="cate-lv2" v-for="(item2, i2) in cateList2" :key="i2">
					<view class="cate-lv2-title">/ {{ item2.cat_name }} /</view>
					<!-- 动态渲染三级分类的列表数据 -->
					<view class="cate-lv3-list">
						<!-- 三级分类 Item 项 -->
						<view
							class="cate-lv3-item"
							v-for="(item3, i3) in item2.children"
							:key="i3"
							@click="gotoGoodsList(item3)"
						>
							<!-- 图片 -->
							<image :src="item3.cat_icon"></image>
							<!-- 文本 -->
							<text>{{ item3.cat_name }}</text>
						</view>
					</view>
				</view>
			</scroll-view>
		</view>
		]
	</view>
</template>

<script>
export default {
	data() {
		return {
			// 当前选中项的索引，默认让第一项被选中
			active: 0,
			wh: 0,
			cateList: [],
			cateList2: [],
			// 滚动条距离顶部的距离
			scrollTop: 0
		}
	},
	onLoad() {
		// 获取当前系统的信息
		const sysInfo = uni.getSystemInfoSync()
		// 为 wh 窗口可用高度动态赋值
		;(this.wh = sysInfo.windowHeight), this.getCateList()
	},
	methods: {
		// 选中项改变的事件处理函数
		activeChanged(i) {
			this.active = i
			this.cateList2 = this.cateList[i].children
			// 让 scrollTop 的值在 0 与 1 之间切换
			this.scrollTop = this.scrollTop === 0 ? 1 : 0
		},
		gotoGoodsList(item3) {
			uni.navigateTo({
				url: '/subpkg/goods_list/goods_list?cid=' + item3.cat_id
			})
		},
		async getCateList() {
			// 发起请求
			const { data: res } = await uni.$http.get('/api/public/v1/categories')
			// 判断是否获取失败
			if (res.meta.status !== 200) return uni.$showMsg()
			// 转存数据
			this.cateList = res.message
			this.cateList2 = res.message[0].children
		}
	}
}
</script>

<style lang="scss">
.scroll-view-container {
	display: flex;

	.left-scroll-view {
		width: 120px;

		.left-scroll-view-item {
			line-height: 60px;
			background-color: #f7f7f7;
			text-align: center;
			font-size: 12px;

			// 激活项的样式
			&.active {
				background-color: #ffffff;
				position: relative;

				// 渲染激活项左侧的红色指示边线
				&::before {
					content: ' ';
					display: block;
					width: 3px;
					height: 30px;
					background-color: #c00000;
					position: absolute;
					left: 0;
					top: 50%;
					transform: translateY(-50%);
				}
			}
		}
	}
}
.cate-lv2-title {
	font-size: 12px;
	font-weight: bold;
	text-align: center;
	padding: 15px 0;
}
.cate-lv3-list {
	display: flex;
	flex-wrap: wrap;

	.cate-lv3-item {
		width: 33.33%;
		margin-bottom: 10px;
		display: flex;
		flex-direction: column;
		align-items: center;

		image {
			width: 60px;
			height: 60px;
		}

		text {
			font-size: 12px;
		}
	}
}
</style>
